1. Field of the Invention
The present invention relates to a thin-film magnetic head which performs a magnetic recording action by a perpendicular magnetic recording scheme, a method of manufacturing the same, a head gimbal assembly, and a hard disk drive.
2. Related Background Art
A hard disk drive has a large recording capacity and is used as the heart of a storage device. The hard disk drive records and reproduces data to/from a hard disk (recording medium) by a thin-film magnetic head.
The thin-film magnetic heads can roughly be classified according to their recording schemes into those of longitudinal magnetic recording type and those of perpendicular magnetic recording type. The longitudinal magnetic recording scheme records data in a (longitudinal) direction within a recording surface of a hard disk (recording medium), while the perpendicular magnetic recording scheme records data such that the direction of recording magnetization formed in the hard disk is made perpendicular to the recording surface. The thin-film magnetic heads of perpendicular magnetic recording type have been considered more promising than those of longitudinal magnetic recording type, since they can realize a much higher recording density than that in the longitudinal magnetic recording scheme, while their recorded hard disks are less susceptible to heat fluctuation.
Meanwhile, a conventional magnetic head of perpendicular magnetic recording type (perpendicular magnetic recording head which will also be referred to as “PMR” in the following) has a magnetic pole layer and a thin-film coil. The PMR has a structure of electromagnet which the thin-film coil are wound around the magnetic pole layer.
A conventional PMR includes a main magnetic pole layer having a magnetic pole end face on a side of a medium-opposing surface opposing a recording medium, a thin-film coil which generates a magnetic field pass through inside of the main magnetic pole layer, and a return magnetic pole layer linked to the main magnetic pole layer via linking part.
Incidentally, the conventional PMR has problems called adjacent track erasure (ATE) and wide area track erasure (WATE). The PMR tilts with respect to the tangent of the track according to the position in the radius direction of the recording medium. This tilt is called skew. When the skew occurs, data recorded on the track adjacent to the track where data will be recorded is sometimes erased by the magnetic flux caused by the recording magnetic field, and this phenomenon is called adjacent track erasure (ATE).
Further, a phenomenon that data recorded on the track disposed at a position distanced by about several μm to several tens of μm from the track where data will be written is erased is WATE. WATE is caused by the fact that a part of the magnetic flux emitted from the main magnetic pole layer and then flowing back to the return magnetic pole layer passes through the shield layer formed in the reproducing head and is emitted from the medium-opposing surface.
A conventionally known technique of improving ATE is, for example, that the shape on the medium opposing surface side of the main magnetic pole layer is formed in a reverse-tapered shape having an upper width larger than a lower width to prevent occurrence of ATE (see, for example, JP 2004-171762 (referred to also as Patent Document 1)).
A known technique of improving WATE is that a backing coil is provided in addition to the thin-film coil which generates the recording magnetic field (see, for example, JP 2006-323932 (referred to also as Patent Document 2), JP 2007-12108 (referred to also as Patent Document 3), JP 2009-252343 (referred to also as Patent Document 4), JP 2010-282717 (referred to also as Patent Document 5)). In the PMR provided with the backing coil, a magnetic flux weakening the magnetic function of the magnetic flux passing through the shield layer is generated by the current flowing through the backing coil. The generation of the magnetic flux improves WATE.
As the PMR provided with the backing coil, there is a conventional PMR 600 illustrated in FIG. 26 for instance. The PMR 600 includes a main magnetic pole layer 601 generating a recording magnetic field, a yoke layer 602 joined to the main magnetic pole layer 601, a first write shield layer 604 joined to the main magnetic pole layer 601 in a medium-opposing surface (hereinafter, referred also to as “ABS”) 603, a second write shield layer 605 joined to the first write shield layer 604 in the ABS 603, a thin-film coil 606 wound around the second write shield layer 605, a shield magnetic pole layer 608 joined to the main magnetic pole layer 601 via a back gap linking part 607, and a backing coil 609 wound around the back gap linking part 607.